THE RESPONSE FUNCTIONS OF THE HEPC LEPC DETECTOR SYSTEM MEASURED AT THE XE L-EDGE REGION/

The Danish Space Research Institute will provide a set of two low ener gy proportional counters (LEPC) and two high energy proportional count ers (HEPC) for the Russian SPECTRUM-X-Gamma mission. The detectors are based upon the technology of the microstrip gas chamber (MSGC). HEPC and LEPC use a Xe/CH4 mixture as the counter gas. The response functio n as well as the pulse height-energy relation for a Xe/CH4 filled MSGC were investigated with monochromatized synchrotron radiation of the B ESSY double crystal monochromator. The detector response functions wer e recorded at similar to 100 selected photon energies in the range fro m 1.8 to 5.9 keV. The response functions were measured with photon ene rgy steps of 5 eV around the Xe L subshells. The average pulse height versus photon energy relation shows clear jumps at the L edges of 55 e V, 25.6 eV and 153. eV at the L(3), L(2) and L(1) shell, respectively. The widths of the pulse height distributions indicate an increase of the Fano factor for Xe at the L absorption edges. These results are in good agreement with earlier predictions. Detailed analysis of the sha pe of the photopeaks as well as of the tail and escape contributions w ill also be presented.